1. Field
The invention is in the field of compound archery bows and specifically in the field of eccentrics and stringing of compound bows.
2. State of the Art
Traditional compound archery bows all include a handle section, upper and lower limbs attached to the handle section extending outwardly therefrom, a pair of eccentrics with an upper eccentric thereof rotatably mounted on the outer end of the upper limb and a lower eccentric rotatably mounted on the outer end of the lower limb, and lacing including a first buss cable extending from one limb of the bow across the bow to the eccentric on the opposite limb, a second buss cable extending from the other limb of the bow across the bow to the eccentric on the opposite limb, and a central stretch extending between the eccentrics to form a bowstring.
With most compound bows, the buss cables are made of an aircraft type braided cable which extend from one bow limb to the eccentric on the opposite limb, about the eccentric and from the eccentric toward the other eccentric to form the ends of the central stretch with a bowstring made of a bowstring material such as dacron extending between the ends of the cable and attached thereto by connectors such as those commonly referred to as tear drops. The cables generally pass through a passageway in the eccentric in which they are secured thereto by a set screw and are wrapped partially around the eccentrics on either side of the passageway. The short lengths of cable extending from the eccentrics to connect with the bowstring are commonly referred to as pigtails. The bowstring material used on compound bows, such as the dacron mentioned, will stretch and with a normal length bowstring, may stretch up to about 1/2 inch under stress.
Bowstrings which are substantially non-stretchable have recently been used with recurve as opposed to traditional compound bows. The non-stretchable bowstring material, sold under the trademark "Fast Flight" by Brownell of Modus, Conn., is made of a polyethylene fiber material sold under the trademark "Spectra" by Allied Fibers, Petersburg, Va., a division of Allied-Signal Inc. The material is very strong and does not substantially stretch and it has been found to increase the performance of the recurve bows on which it is used.
While the "Spectra" string material has been used with recurve bows, it has not been found usable on the traditional compound bows where the bowstring is attached to pigtails as described above, and, in fact, such string material now generally carries a label warning against use on that type of compound bow. The reason for this is that there is a tendency when using "Spectra" bowstring material, particularly if the bow is misfired or is accidentally dry fired, i.e. the string is let go from drawn position without an arrow in place, for the teardrops which secure the bowstring to the pigtails extending from the eccentrics to break off or for the cables themselves to break. In such instance, the broken end of the cable may whip around and strike the bow limb and in some cases severely damage the bow limb. The reason for this breakage is not known. However, when a bow is fired, the limbs of the bow move rapidly forwardly until they are suddenly stopped by the bowstring reaching its braced position and preventing any further forward movement. This sudden stopping of the limbs puts a large amount of stress on the bowstring, its attachment to the cables and on the cables. A string with some stretch will stretch slightly to absorb the sudden stop of the limbs. It is beleived that the substantially non-stretch nature of the "Spectra" string which does not absorb the shock of the stop in order to lessen the sudden stress on the teardrops or other string connectors or on the cables causes too much stress on the connectors and therefore causes them to break off and create an undesirable situation.
While U.S. Pat. Nos. 4,368,718, 4,401,097 and 4,478,203 show a unique eccentric configuration which includes a hook member on the eccentric over which the bowstring is wrapped and shows a bowstring separate from the buss cables and which is secured directly to the eccentric, such direct separate connection is used so that the special eccentric may be used. The bowstring used is still standard stretchable bowstring material. Further, the buss cables are standard cables secured to the eccentrics in the standard manner with a set screw, or, in U.S. Pat. No. 4,478,203, by means of an anchor member secured to the end of the buss cable. Applicants are not aware of any compound bows with more conventionally shaped eccentrics where the bowstrings are connected directly to the eccentrics separately from the buss cables.